Polymeric materials play an important role in modern materials science. Synthetic condensation polymers (e.g., materials having organosulfone, organosulfate, organocarbonate, organocarbamate, organourea, or organic ester-type polymeric backbones) are utilized in a variety of products and industries, including, for example, packaging, high performance engineering materials, medical prostheses and implants, optics, and consumer plastic goods. There is an ongoing need for new methods of preparing polymeric materials, particularly solid polymers (e.g., plastics), including materials for high value, specialty applications (e.g., medical prostheses and implants, engineering materials, or optics). The polymerization methods and polymers described herein address these needs.
A handful of reactions are at the core of multimillion-ton polymer industry. Most commodity polymers are synthesized from olefins by forming carbon-carbon backbones, whereas engineering polymers are commonly prepared via condensation reactions of monomers containing an activated carbonyl group or its equivalent and a suitable nucleophile, thus forming carbon-heteroatom linkages. Polyesters, polyamides, polyurethanes, and polyimides are produced in this manner. Despite the variety of backbone structures, polymers containing sulfur(VI) “—SO2—” connectors are virtually absent from the literature and barely used in industrial applications, with the exception of polysulfones, in which the sulfone group is already present in the monomers (see e.g., Garbassi, in Kirk-Othmer Encyclopedia of Chemical Technology; Fifth Edition; John Wiley & Sons: 2007; Vol. 10).
Unsurprisingly, most reported attempts to synthesize sulfur(VI)-containing polymers relied on reactions mimicking carbonyl group-based condensations, i.e. reactions of sulfonyl chlorides with nucleophiles (see e.g., (a) Goldberg et al., U.S. Pat. No. 3,236,808; (b) Firth, U.S. Pat. No. 3,895,045; (c) Thomson et al., J. Pol. Sci., Part A 1964, 2: 1051; (d) Worket et al., Polym. Sci., Part A: Polym. Chem. 1968, 6: 2022; (e) Schlott et al., in Addition and Condensation Polymerization Processes; American Chemical Society: 1969; 91:703-716) and, to a much lesser extent, Friedel-Crafts sulfonylations (see e.g., Cudby et al., Polymer 1965, 6:589). Despite the attractive properties of polymers obtained by those methods, such as good thermal and hydrolytic stability and mechanical resilience (see Thompson et al., id.; Worket et al., id.; and Schlott et al., id.), the unselective reactivity of sulfur(VI) chlorides, which are susceptible to hydrolysis and participate in facile redox transformations, especially chlorinations, significantly limit utility of these methods and materials.
Reactions of many silylated and fluorinated compounds are known in organic synthesis and also in polymer chemistry. In 1983, Kricheldorf introduced the “silyl method” for the synthesis of polyaryl ethers, taking advantage of the strength of the Si—F bond and the innocuous nature of the silyl fluoride byproducts (Kricheldorf et al., J. Pol. Sci.: Pol. Chem. Ed. 1983, 21:2283; Bier et al., U.S. Pat. No. 4,474,932). In 2008, Gembus demonstrated that sulfonyl fluorides (R—SO2F) react with silyl ethers in the presence of a catalytic amount of DBU, producing aryl sulfonates (Gembus et al., Synlett. 2008, 1463).
Sulfur(VI) fluorides, in particular sulfuryl fluoride (SO2F2) and its monofluorinated derivatives, sulfonyl (RSO2—F) fluorides, sulfamoyl (R2NSO2—F) fluorides, and fluorosulfates (ROSO2—F), in which R is an organic moiety, stand in stark contrast to other sulfur(VI) halides. These sulfur oxofluorides are much more hydrolytically stable, redox silent, and do not act as halogenating agents. Nevertheless, their selective reactivity can be revealed when an appropriate nucleophile is presented under the right conditions. In the early 1970s, Firth prepared poly(arylsulfate)bisphenol A (BPA) polymers from fluorosulfates of BPA (obtained from BPA and SO2F2), and disodium salts of bisphenols (see, e.g., Firth, J. Pol. Sci., Part B 1972, 10:637; and Firth, U.S. Pat. No. 3,733,304). The polymerization required prolonged heating and produced a significant quantity of byproduct (12 to 22%) which Firth indicated to be cyclic oligomers. Removal of the byproduct required repeated precipitation of the polymer from dimethylformamide (DMF) into methanol.
There is an ongoing need for new polymerization methods that are versatile and capable of producing a wide variety of polymer structures, including materials formally considered to be condensation polymers, under relatively mild and scalable conditions. There also is a need for new polymers, e.g., for structural, packaging, and fiber applications, and for polymers from processes that tolerate monomers bearing extra, non-interfering groups, which can be functionalized for specialty applications. The methods and polymer described herein address these needs. In addition to providing a practical route to polymers with useful properties, the exceptionally facile synthesis of organosulfates described herein highlights the underappreciated potential of the sulfate connector, in particular, in organic chemistry, as well as unique reactivity features of sulfur(VI) oxofluorides. The polymers and methods described herein should find immediate applications across different disciplines.